Stool specimens submitted to Charity Hospital and the HIV Outpatient Clinic, New Orleans, LA from HIV-infected individuals with abdominal pain and/or chronic diarrhea were examined for the presence of microsporidia by histochemistry and PCR-based methods. During 1998, 48 of 378 (12.7%) stool specimens were positive for microsporidia by histochemical staining compared with prevalence rates of 16% in 1997 and 35% in 1996. Persons receiving protease inhibitors and those with >100 CD4+ T cells/ul blood were more likely to have resolved their microsporidiosis at the 6-month follow-up visit compared with those not receiving protease inhibitiors or with lower levels of CD4+ T cells. Additional risk factors identified for microsporidiosis included exposure to freshwater or seawater fish, and living in a rural setting. In addition, microsporidiosis is believed to be zoonotic since several species of microsporidia identified in humans are also known to infect other animals. Several incidenta l case reports support this hypothesis. Encephalitozoon cuniculi strain III (originally identified in domestic dogs) was identified in AIDS patients in the U.S.A., and a recent outbreak of E. cuniculi has been reported in another litter of dogs in MN. Urine and serum from the pet owners are currently being examined for microsporidia, as well, to determine if transmission from pets to owners (or vice versa) may have occurred. Encephalitozoon hellem, which had only been identified in AIDS patients, was recently identified in psittacine birds in an aviary in Mississippi and from archival avian tissues in Texas. A recent outbreak of microsporidiosis in tanagers is being evaluated to determine if birds other than psittacines may harbor this species. A new Encephalitozoon species in African lizards (skinks) was characterized and given the name E. lacertae (n.sp.). FUNDING NIH; 1RO1 AI39968-03 (E.S. Didier, P.I.); 08/01/96-07/31/99; $163,397 (year three directs; 100% to RPRC) PUBLICATIONS Abstracts Didier, E.S., K. Dascomb, L.B. Rogers, P. Kissinger, and R. Clark. 1998. Diagnostic and epidemiological features of microsporidiosis in AIDS. Abstract at the Keystone Symposium on Opportunistic Infections in AIDS, Keystone, CO (abstract Y2-202). Snowden, K, E.S. Didier, and D. Phalen. 1998. What is the source of Encephalitozoon infections in immunocompromised humans? 49th Ann. Southwest Conference on Disease in Nature Transmissible to Man. College Station, TX (abstract). Snowden, K., D. Phalen, and E.S. Didier. 1998 Where are the reservoirs of human microsporidial infections? Second European Congr. Trop. Med., Liverpool, U.K. (abstract 438) and Amer. J. Trop. Med. Hyg. 59:302 (abstract 554). Peer-reviewed publications Boldorini, R., G. Monga, A. Tosoni, E.S. Didier, and J.M. Orenstein. 1998. Renal Encephalitozoon intestinalis infection in a patient with AIDS Post-mortem identification by means of transmission electron microscopy and PCR. Virch. Arch. 432:535-539. Koudela, B, E.S. Didier, L.B. Rogers, D. Modry, and S. Kucerova. 1998. Intestinal microsporidiosis in African skinks Mabuya perrotetii. Folia Parasitol. 45:149-155. Reviews and book chapters Didier, E.S., K.A. Snowden, J.A. Shadduck. 1998. The biology of Microsporidian species infecting mammals. Adv. Parasitol. 40:279-316. Didier, E.S. 1998. State-of-the-Art Clinical Article Microsporidiosis. Clin. Infect. Dis. 27:1-7. Soave, R. and E.S. Didier. 1999. Cryptosporidium and Microsporidium. In Textbook of AIDS Medicine (2nd ed.). T.C. Merigan, J.G. Bartlett, and D. Bolognesi (eds.). Williams and Wilkins, Baltimore, MD. pp. 327-356. Didier, E.S. and G.T. Bessinger. 1999. Host-parasite relationships in microsporidiosis animal models and immunology. In:The Microsporidia and Microsporidiosis. M. Wittner (ed.). American Society for Microbiology, Washington, D.C. pp. 225-257. Didier, E.S. 1999. Immunology of Microsporidiosis. In Contributions to Microbiology. F. Petry (ed). S. Karger AG, Basel, Switzerland (in press).